Grinding machine



Dec. 11, 1945,

S. E. WOODBURY I GRINDING- MACHINE 4 S heets-Sheet 1 Filed Aug. 26, 1943s. E. WOODBURY G-RINDING MACHINE I Filed Aug. 26, 1943 4 Sheets-Sheet 2Dec. 11, 1945. s, WQQDBURY 2,390,978

GRINDING MACHINE Filed Aug. '26, 1943 -4 SheetS Shet' s Fil ed Aug. '26,1945 4 Sheets-Sheet 4 m 14 m m 2 1 i-"econ? 11, 1

Stephen E.

t 18 Claims.

This invention relates to grinding machines and consists in certainimprovements increasing the efllciency, precision and safety "of suchmachines in operation and their-convenience of control by the operator.Surface grinders a? heretofore constructed have included-a work-carryingslide or table arranged ditions are thus created which are mostfavorable to travel back and forth longitudinally beneath 5 PATENTOFFICE GRINDING MACHINE Woodbury; Beverly, Mass, assignor to Reid 1Brothers Company, Inc., Beverly, Mesa, a corporation of MassachusettsApplication August, 26, 1943, Serial No. 500,078

but variable interval immediately prior to the instant of actualreversal'and provide means for regulating the interval of over runningby mothe grinding wheel, and cross feed mechanism for shifting the pathof the table. transversely after each reversal of its longitudinaltravel.

An important feature of the present invention consists in mechanismconstructed and arranged to cause operation of the cross feed mechanismin anticipation of each such point of reversal of the table, so that thecross feeding step may be effected during the final portion of the tabletravel, after the wheel leaves the work and before the direction oftable travel is reversed. The result is that the work is brought to thewheel in a straight line movement prior to each grinding stroke of themachine and there is no traverse movement of the wheel and work duringthe grinding stroke. The amount of metal removed by the wheel istherefore. substantially uniform from one end of the stroke to theother, and confor great accuracy of operation.

The efficiency of the machine is also improved cross feeding operation,time that would otherwise be wasted between consecutive grindingstrokes. On the contrary, my invention anticipates the point of tablemovement reversal and initiates the cross feeding operation as soon asthe.

wheel passes off the work. To this end'I employ an oscillatory sectorwhich is swung. through a predetermined angle by the work table itselfnear each end of its stroke for controlling the reversing mechanism andI utilize an intermediate portion of the sector movement for throwingthe.

cross feed mechanism into and out of operation.

Another important feature of my invention consists in utilizing andcontrolling the momentum of V the cross feed mechanism to extend thecross feeding operation into the initial portion of the reverse travelof the work table after each point of mentum so that the cross feedingoperation may extend somewhat into the period of reverse travel of thetable, although of course never up to the point in which the work meetsthe grinding wheel.

Another important feature of my invention consists in safety mechanismfor terminating the cross feeding operation independently of its regularautomatic control in the normal operation of the grinding machine, andrestricting the cross feeding operation under all conditionsto ana'mplitude that will prevent possible damage tothe work ordisorganization of the machine. To this end I provide an actuatingmember, shown as a rocker, which is arranged to assume a predeterminedinitial position at the end of every cross feeding operation and to beclutched or connected to the cross feeding mechanism at the beginnin ofeach operation. A safety switch is provided in position to be engaged bythis actuating member to break the circuit and stop the cross feed motorin case the cross feeding operation is unduly extended by any accidentor oversight.

While the invention is herein disclosed in this thereof selected forpurposes of illustration and 7 shown in the accompanying drawings inwhich,

Fig. 1 is a view in perspective showing the general organization oftheme-chine,

Fig. 2 is a view in perspective of mechanism below the table of themachine, 6 v Fig. 3 is a view in perspective of safety mocha:

nsim for limiting the extent of cross feed,

.Fig. 4 is a view in longitudinal section of another portion of the samemechanism,

Fig. 5 is a, similar view of a portion of the motor driven crossfeedshaft,

Fig. 6 is a view in elevation of portions of the machine showingmechanism for controlling and adjusting the extent of cross feed,

Fig. 7 is a fragmentary view in perspective of the same mechanism,

Fig. 8 is a view in perspective of the controlling disk as seen frombeneath.

, cross feed mechanism,

Fig; 12 is a wiring diagram of the machine,

Fig. 13 is a diagrammatic view illustrating the timing of the cross feedoperation, and

Figs. 14 and 15 are diagrams of the table movements.

In its general organization the illustrated machine includes a box frameI from the rear side of which rises an upright column or post II. Thegrinding wheel I8, together with its spindle and individual drivingmotor 82, are mounted for vertical adjustment in a slide carriermovably' mounted in the post II. The operative position of the grindingwheel is adjusted and controlled by V a hand wheel Ill,convenientlyprojecting from the front wall of the machine frame I0.

Splined on the shaft assume the shaft and clutched to the hub of thehand wheel 28, whereupon longitudinal feed can be effected as a manualoperation.

The pinion 23, notwithstanding its shifting with the sleeve 22, alwaysremains in mesh with a large gear 30 fast on a grooved transverse shaftH which is journalled in bearingsprovided in the front and rear walls ofthe machine frame It. 3| is a collar 39 formed in tegral with a sprocketwheel 33. The collar '4 is embraced between the walls of a yoke itdepending from the lower surface of the crdss slide I3, as shown in Fig.10. When the slide is given a cross feeding movement, as will bepresently The connecting mechanism is not herein shown since it forms nopart of the present inventio but is well known in the industry.

In the top of the machine frame III are provided spaced transverse waysI2 and I9, .both herein shown as V-shaped, but not necessarily so, andin these ways rests the cross slide It. The

slide I3 is provided with longitudinal ways iii in its upper face towardthe rear and in these slides the elongated work table It carrying anadjustably mounted magnetic chuck I'I upon which the work to be groundby the wheel I8 is clamped. I

' Longitudinal feed Longitudinal feed of the worktable I8 back andforthon the cross slide I3 is effected through outer end is suitablyjournalled in the front wall of the machine frame Ill. The shaft carriesa loose sleeve 22 formed integral at one end with a'pinion 23 and at theother with a grooved ring in which rests a shipper segment 24. Thesleeve also has clutch teeth projecting from its oppos'ite ends. Thesegment 2| extends outwardly.

and downwardly being provided with a shank portion which is guided fortransverse movement on a guide rod 25 disposed parallel to the shaft 20.This shank portion in turn has a pin and slot connection with the shortinner arm 26 of a bell crank lever (see Fig. 10) pivotally mounted torock on a short shaft 28 projecting from the left side wall of themachine frame. The

other and longer arm of the bell crank lever comprises a handle 21located outside the wall of the frame. When the handle 21 is swung. inone direction the sleeve 22 is shifted toward the right I .as seen inFig. '2 and is positively clutched to the shaft 20 through the collar2i. Under these conditions rotation of the shaft 20 to effect thelongitudinal feed of the work table I8 is carried out by power from themotor. A latch it maintains this power connection.- until released bythe operation. On the other hand. when the handle 21 is swung in theopposite direction, the sleeve 2: is shifted toward the left, unclutched1mm operative connection between the two is at all times maintained.

A sprocket chain 36 runs about the sprocket wheel 33,'upwardly overidler rolls 35 and 3G in the slide I3 and thence in opposite directionsto points of connection with the work table Ed ad" jacent its oppositeends and in its under face. It will be apparent; therefore, thatrotation of the shaft 20 either manually or by power will, through thesprocket connections above described, im art a longitudinal feedingmovement to the work table It in a direction depending on the direction.in which the said shaft 20 is rotated.

In the power operation of the machine the length of work table movementand its points of reversal are determined bya pair of dogs 4| and 42adjustably mounted in an undercut slot 0 provided in the front edge ofthe table I6. as shown in Fig. 1. To this end a sector 63 is mounted torock on a horizontal axis with a sh'aft 59 projecting forwardly from thecasing of a reversing switch 49 secured to one side of the cross slideI3. The shaft 59 projects forwardly and is provided with a'knurledoperating head 48 at its forward end. A pin 44 projects forwardly fromone corner of the sector into the path of the dog 4! and a pin 45'projects rearwardly from the other corner of the sector into the path ofthe dog 62. When either dog I or 42 rocks the sector it the switch 59 isthrown and current in the longitudinal feed motor is reversed and withit the direction of feeding movement of the table.

The same result may be obtained manually by I turning the operating head48 at any time when the sector 43 is clear of the dogs ll and 42.

At either end the table I6 carries a wedge cam I08, one only being shownin Figs. 6 and 9, which cooperates with a limit switch IIIE mounted onone side of the casing of the reversing switch 09. The switch I01 isnormally closed and is opened by the depression of aroll-carrying,plunger,,l09 standing in the path of the wedge cams I08.Accordingly, if for any reason the table fails to reverse, one or theother of the cams I08 will de press the plunger I05, throw the switchI01 and stop the table motor, as will be presently explained. In thenormal operation of the machine, of course, the table is reversed beforethe cams I08 reach the position of the plunger I00.

It will be understood that the general construc tion of the machineheretofore described is no part of my invention but that the operationand controlof its elements and the mechanism therefor npwto be describedis the subject matter of my invention.

Cross feed The individual cross feed motor :1 is shown an attached tothe right hand wall of the machine through a pair of coupling collars 86to a shaft 8| journaled in a bracket 80 mounted within the machine frameI0. The shaft 8| carries a worm 82 which is always in mesh with anelongated pinion 60 mounted on a transverse shaft 6| journaled in a yoke62 within the enclosure of the frame I0.

The elongated pinion 60 is always in mesh with a pinion 52 fast on ashaft which carries the cross feed lead screw 53 threaded into anelongated nut 54. The nut 54 is rotatably held in the front wall of themachine frame and is connected to a hand Wheel 55 projecting from thewall in convenient reach of the operator. At its inner end the shaft 5|is connected through,

thrust bearings to a, second yoke 50 projecting downwardly from thelower face of tho cross slide I3 at the right hand side of the yoke I4already mentioned. This connection is the point of application of thecross feeding mechanism to the cross slide. In cross feeding in eitherdirection movement is derived from manual rotation of the hand wheel 56and nut 54 or from power rotation in the nut 54 of the screw 53, throughits connections with the shaft 8| and the motor 81.-

W iring diagram The grinding wheel I1, the work table I 6,and

the cross feed slide I3 are all operated by individ- I motor 32.

ual motors connected and controlled by the system of wiring shown in thediagram of Fig. 12. Three phase power is supplied on the line switch I25from whence it is tapped direct to the spindle From the line switchthree wires also lead to the table motor, two of them through a handcontrolled two pole switch 19. The reversing switch 49 is included intwo of three wires of the table motor and this switch is operated by thesector 43.

A pilot or relay circuit extends between the two outside terminals ofthe line switch. -This includes a connection I26 to the starting switchI I1. When the switch I I1 is closed current flows in the relay circuitthrough the normally closed stopping switch M9, the normally closedsafety switch I01, the normally closed feed limiting 1 switch 18 and thesolenoid H8. The olenoid I I8 automatically closes the line switchwhereupon the table motor may be started by closing the hand operatedswitch I9. Meanwhile current in the relay circuit flows in the branchI21 and,

the starting switch H1 remains open. Under' operating conditions,therefore, the line switch may be opened automatically by throwing thestopping switch II 9, or by the opening of the safety switch I01 byaction of the dog I08, or by operation of 'the feed limiting switch 18by the safety cam 66.

Three wires, two of them led through a. relay controlled switch 16, alsolead to the cross feed motor 81. In this circuit is included the handoperated reversing switch I I0 for controlling the direction of crossfeeding.

The wiring includes a second relay circuit for controlling the crossfeed switch 16. This second relay circuit includes the switch 90operated by the cam 46 and the solenoid 15 which when energizedclosesswitch 16 to the cross feed motor.

Current flows in this circuit only during the short double pole switch16 under the control of a. solefeed slide, as shown in Fig. 1, where itmay be hold 15 in a pilot or relay circuit which includes a. normallyclosing switch 90. when the switch 16 is closed the motor 81 operatesand the cross feeding operation occurs. Theswitch 16 is held closed onlywhile the plunger 41 of the pilot switch is allowed to remain in itsuppermost position. The plunger 41 is controlled by a cam 46 keyed tothe shaft 59 and moving with the sector 43. It has a. fiat side in itsperiphery and is arranged symmetrically with respect tothe sector,. thatis, when the sector standsvertically the flat side of the cam 46 isdisposed horizontally, permitting the plunger 41 to rise to its fullestextent in the cycle, tending to close the relay circuit and close theswitch 16. When the cam 46 is swung in either direction out of its midposition the pilot switch plunger 41 is depressed at a time and for aninterval depending upon the vertical position of the pilot switch 90,which, as will presently be explained, is mounted for verticaladjustment under the very sensitive control of the operator. The mode ofoperation thus explained is illustrated diagrammatically in Fig. 13. Themovement of the sector 43 to effect a complete reversal of tablemovement takes place through the angle A. The cam 46 permits the crossfeed motor to operate during the angle B,

for an intermediate setting of the pilot switch during only thatfraction of the swing of the sector 43 (represented by the angle B or C)on each side of its mid position in which the plunger 41 is allowed toremain undepressed. A very slight depression of the plunger 41 issufiicient to break the circuit in the switch 90 and all furthermovement of plunger 41 is merely idlerbvertravel.

The switch 90 has a vertical guide pin 9| projecting upwardly from itscasing and arranged to slide in the horizontal arms of a guide bracket92 fast to the casing of the switch 49. The guide pin ,9I -carries agrooved collar 93 into which projects a pin carried by a substantiallyhorizontal arm 94. The arm 94 is keyed to the forward end of a shortshaft 95 which is journaled to rock in the webs of the cross feed slideI3 as shown in Fig. 7. 'At an intermediate point the shaft 95 carries ashort arm 96 against which secured to the rear of the switch 90 and tothe side of the casing of the switch 49 also tends to lift the switch90. The spring I05 is best shown in Fig. 6. At its rear end the shaft-95carries av block 91 having a rearwardly projecting pin which engages ashort arm 98 fast to the rear end of a long horizontal shaft 99 alsojournaled in webs of the feed slide I3. The shaft 99 goes through to thefront edge of the feed slide and just within the front flange thereof isprovided with a limit stop I00 and an arm I0l extending in asubstantially horizontal direction toward the left as seen in Figs. 6and '7. A pin I 02 rests upon the free end of the arm IM and passesupwardly freely through an aperture in the feed slide. It is received ina. circular groove with a spiral bottom surface cut in the under face ofa I graduated disk I03 which is mounted to-rotate freely in the forwardright hand comer of the conveniently reached by the operator.

It will be seen that rotation of the disk I03 gives the operator quickand delicate control of.

its uppermost position as shown in full lines in Fig. 6. In thisposition of the switch 90 the plungerfi'l is not permitted to reach itsmost elevated position and no cross feed occurs. In

other words the angle B has become zero. Now,

when the disk I03 is turned to some such reading as 0.005 the switch 90is slightly lowered. Accordingly when the cam 46 is rocked theplungerfil is elevated to its switch closing position for only aninstant during the swing of the sector 43. This might be represented bythe small angle B in the diagram of Fig. 13.

From this it will be seen that the pilot switch is allowed to close onlyjust before the sector reaches its mid position and is again opened Justafter the sector passes its mid position. The full ower cross feed istherefore effected just prior to and in anticipation of the reversal ofthe table movement. This action is indicated by the diagram of Fig. 14where the lin I20 indicates the movement of the table I6 toward theright and the line I22 its movement toward the left after reversal. Thecross feed is effected prior to the actual point of reversal, while thetable movement is represented by the line I2l. As the table approachesthe point of reversal in its movement toward the left the cross feed isrepresented as taking place in the line I23.

, Now if the operator desires to increase the amplitude of the crossfeed he has only to turn the graduated disk I03 forcing downwardly thepin I02. This has theeifect of rocking the arm IOI downwardly and movingthe switch 90 downwardly against the action of th springs H3 and I05into some such position as indicated in dotted lines in Fig. 6. Theeffect of this adjustment is to increasethe interval of cross feedbecausethe cam 46 has to rock less before it releases the plunger 41 formovement into its upper or closedswitch position and further before itdepresses it to break the relay circuit. The further the disk I03 isturned the greater is the extent of the cross feed and the steeper theangle of the lines I2I and I23 in the diagram of Fig. 12. The switch 90cannot be set so low that the corner of the fiat side of the cam in theextreme positions The friction on the disk as may be adjusted sothat theshaft will practically come to a dead stop the instant the switch 00 isopened and under such conditions the table movement is that shown in thediagram of Fig. 14. However, by relaxing the friction on the disk 85 toa limited extent the momentum of the moving parts may be permitted tocarry the shaft BI a few turns ahead after power has been cut off fromthe motor 01. In this way'a portion of the cross feed may be carriedbeyond the point of actual table reversal and take place during theinitial portion of its reverse longitudinal travel.

This mode of machine operation is indicated in the diagram of Fig. 15where I 30 indicates table movement toward the right, power cross feedoccurs while the table moves in the line III and momentum cross feedoccurs while the table moves toward the left in the line I32 prior toits straight line feed toward the left in the line I32. It is plain thatthe momentum cross feed balances the power cross feed in the cycle ofthe machine,

' both occurring while the grinding wheel is oil cannot rest on plunger41, therefore the cross feed cannot be set to run continuously but mustfeed only near the ends of the table travel.

Hitherto it has been assumed that the cross feed takes place only duringthe power operation of the motor 81' and it is a fact that this is adesirable and satisfactory mode of operation.

However, I increase range of usefulness of the machine by provi g insome cases for a further cross feed which is effective after the motoris cutoff by the controlled momentum of the parts it has set inoperation.

The shaft 8i carries a friction disk 85 which runs between cylindricalfriction members 83 and 84 yielding and adjustably held together,

and locked against rotation by an anchor screw 88 threaded into the baseof the bracket 80. The purpose of this friction mechanism is to providea' drag on the shaft BI that will reduce the tendency of the shaftto-spin when its actuating current is cut off, that is, to limitover-running in the cross feedhig operation.

the work. I

, Cross feed safety stop The shaft BI, which is driven by the worm s2friction face corresponding to the leather friction face 64. It alsocarries a triangular safety cam 68 and a counterweight 01 which holdsthe cam 66 normally in upright position. In the hub of the frictionmember 65 is carried a hardened ball adapted to be engaged byan'upstanding spring ,arm 68 fast to the machine frame. The arm 00 isoscillated to apply clutching engagement to the rocking member 65through a horizontal rod 69 which is'connected at its'left hand end, asshown in Figs. 2 and 3, to a vertical arm' 10 loosely mounted in theleft hand branch of the bracket 62.

In a bearing block II carried by this bracket is Journalled a horizontalshaft having a short upstanding arm I2 carrying an adjustable contactscrew which engages the arm I0. At the other end of this shaft is a longarm I3 which rests on a pin Id projecting outwardly from the plunger ofa solenoid 15 which is primarily controlled by the relay switch asalready described in detail, but which is also controlled indirectly bythe before mentioned limiting relay switch I0. As already stated, theswitch I8 controls the solenoid II8 which operates the main switch I25,with the result that the opening of the switch I8 opens the maincircuit, thus de-' energizing the solenoid I5, even though the switch 90should remain closed. The'switch I8 is located with its operatingplunger 11 beneath and in operativerelation to the triangular cam 06.The triangular cam 66 is normally caused to stand in vertical positionby its counterweight l1 and the relay current flowing in the solenoid I5normally holds the arm I4 in its elevated position so that the arm 68,through the connections described, is pressed against the end of therocker member 65 which is thus clutched to the friction 'end of theshaft Bil This member has an inner ascoms completion of each crossfeeding step, the switch ll is opened as already described and thesolenoid I is de-energircd. thus releasing the rocker member it from theshaft SI and permitting the cam 68 to return by gravity to its elevatedposition. Since the longest single cross feed step ever utilized inpractice does not require more feeding movement is not properlyterminated,

current continues to flow in the relay circuit and the cam 68 continuesto travel till it depresses the plunger 16 and breaks the circuit at theswitch 18 allowing the line switch "to open and bringing the table to animmediate stop.

The shaft 53 as shown inFig. 11 is mounted in ball thrust bearings inthe yoke 50 on the under side of the cross slide. The pinion 52 is faston this shaft having a press fit thereon. The threaded portion of theshaft turns in the long nut El. When it has been turned enough to moveup and engage the inner end of the nut, then the nut begins to spin withthe pinion and the shaft 53 so that no. cross feed takes place. The handwheel 56 is fastened to the nut 54 by a set screw so that the hand wheel56 will spin idly when no cross feed is taking place. Under thesecircumstances the inside races of the roller bearings in the frame Inturn with the shaft. The

shaft itself is shouldered down to present a thrust collar for the ballthrust bearings. When the threaded shaft 53 has been turned in the otherdirection sumciently to bring the cross slide I3 to its rearward limitof movement, frictional engagement between the shaft and the nut is in-My improved grinder has also outstanding safety and conveniencefeatures. To enumerate a few, all controls are now arranged so that-theoperator can adjust the machine while-itziis running without needing totouch any moving part. The adjustment for extent of cross feed can bechanged as often and as much as desired i in perfect safety while the.grinder is running, whereas previously this required that the grindermust be stopped and the adjustment made on parts that are normally inmotion The hand feed is retained in such a way that it is not activeuntil needed and thencan be used without giving any thought to theautomatic anticipative cross feed. Moreover the automatic cross feedautomatically goes out of 'commission at each end of the limit of travelof the cross slide in either direction.

Having thus disclosed my invention and described in detail a specificembodiment thereof I movement, a cross feed electric motor, means fordirecting an operatingcurrent to said motor for starting it, andmechanism thereupon operated by said motor for imparting a transversefeeding step to th table'in anticipation of andbefore its reversal andfor stopping said motor at the conclusion of each cross feeding step.

and a work table,'cross feed mechanism for the table, longitudinal feedmechanism for the table,

creased to such an extent that the nut turns with the shaft in theroller bearing, thus permitting continued rotation of the shaft 53without damage.

The advantages of my invention will be more fully appreciated when'it isremembered that in surface grinders now available on the market the.table carrying the work reverses its motion at the end of the stroke inorder that the crossslide may be fed over so the grinding wheel will cuta new path. Therefore, the cross feeding takes place after the work hasreturned under the wheel for several inches, whereas it shouldpreferably have occurred before the work arrived at the wheel.

My improvement consists in utilizing the time after the work has leftthe. wheel up to when it returns to the wheel to do the cross-slidefeeding. This is usually about twice three-quarters of an inch of tabletravel. When all the feeding is done in this space, the wheel cuts a newpath over the entire length of the work. Without this improveme e wheelreturns to the work along the path dy cut and so does not grind untifthe work is carried overby the feed of the cross slide several inchesfrom the beginning. Also, as the work comes out from the wheel the metalthat has been left is now groundaway as an extra amount. This loads thewheel to its limit, for no reason other than that this isneveroverloaded at any point.

. and a work taiblaecross, feed mechanism for the table, a crosselectric motor for operating the same, longitudinal feed mechanism forthe table, mechanism timed in its operation by the longitudinal movementof the table for reversing the longitudinal feed mechanism, forstartlngsaid cross feed motor to initiate the action of said I crossfeed mechanism and for stopping it at the conclusion of each crossfeeding step, and means adjustable by the operator for regulating theextent of each cross feed operation.

4. A surface grinder having a grinding wheel and a work table, crossfeed mechanism for the I table, a cross feed electric motor foroperating the same, longitudinal feedmechanism for the table, a sectoroscillated by the longitudinal movement of thetable for reversing thefongi- ,tudinal feed mechanism, a cam symmetrically disposed withrespect to said sector and movable therewith for starting said crossfeed motor to initiate the action of said cross feed mechanism inanticipationio'f and before the reversal of the table in eachstroke, andmeans adjustable by and arranged to start said cross feed'moton at thesector movement.

predetermined points in its travel before the end of each reciprocation,and a controlling device. .located on the cross slide in convenientreach of the operator for advancing or delaying the action of the worktable on the cross feedmechamsm.

6. In a grinder, a cross feed slide, an electric motor for operating thecross'feed slide, a work table and electrically operated mechanism formoving said table longitudinally back and forth 10 on .the cross slide,spaced dogs carried by the work table, a rocker member located in thepath of said dogs and movable by them for reversin said work tablemechanism, a cam operated by said rocker member, electrical means underthe '7. In a grinder, a cross reed slide and a work table carriedthereby, electrically operated mechanism-for moving said table back andforth in said deed slide, cross feed mechanism, an electric motorconnected to operate the cross feed mechanism and arranged to be throwninto periodic action by the work table prior to each reversal, agraduated disk located on the'cross feed slide within-convenient reachof the operator, and means operated thereby for controlling the lengthof time the cross feed motor remains in o'peration at each reversal.

8. In a grinder having a table mounted to reciprocate on a movable crossfeed slide and motor operated mechanism for eifecting tablereciprocation and cr f movements, a ro r during a short interval beforeeach point of table for bodily moving the switch to vary its time of 40,

action.

9. In a grinder having a table mounted to reciprocate on a movable crossfeed slide, and motor operated mechanism for efiecting tablereciprocation and cross feed movements, a rocker oscillated :by thetable prior to each reversal of its reciprocation, a switch operated bysaid rocker for timing the cross feed movement, spring means tending tomove said switch and rocker toward each other, a graduated disk'locatedin the '50 grinder within convenient reach of the operator, andconnections between the disk and switch for positively moving the saidswitch away from the? rocker.

10. In a grinding machine having a reciprocatory table, a cross feedslide carrying the table, and individual motors and connecting mechanismfor the table and cross feed, an oscillatory sector mounted to be swungby the table and controlling the reversal thereof, and means forthrowing the g0 cross reed motor and its connections into operationduring a predetermined fractional part of 11. In a grinding machinehaving a reciprocatory table, a cross feed slide carrying the table,

and individual motors and connecting mechanisms for the table and crossfeed slide, an 05-- cillatory sector mounted to be swung in opposite,directions by the table from an inclined position on one side of aperpendicular mid-position to an by the table and determining in itsmovements inclined position on the otherside thereof and to effectreversal of the table motor in its said movement, andcam-controlledmechanism for throwing the cross feed motor, into operation positionand, throughout an angle lessthan that oi its full oscillation.

12. In a grinding machine having a reciprocatory table,'a cross feedslide carrying the table,

and individual motors and connecting mechanisms for the table and crossfeed, means for supplying operating current to the cross ieed motor at apredetermined but variable interval before the point of table reversaland for cutting of! its current before actual reversal takes place, andadjustable means for timing the overrunning of said motor, whereby thecross feeding operation may extend into the initial portion of thereverse travel of the table.

13. In a grinding machine having a reciprocatory table, a cross feedslide carrying the table, and individual motors and connectingmechanisms for the table and cross feed slide, a switch for controllingthe flow of operating current to the cross feed motor arranged to beclosed and opened in anticipation of the table reversal atcach end ofthe table travel, and adjustable means acting on the connectingmechanism of the cross feed motor to limit over-running of the motor toa time of travel of the table in reverse no reater than its travelpriorto reversal.

14. In a grinding machine having a reciprocatory table, a cross feedslide carrying the table, and individual motors and connectingmechanisms for the table and cross feed slide, a switch for controllingthe flow of operating current to the cross feed motor, connectionsincluding a motor driven shaft for transversely moving the cross feedslide, means for closing the switch reversal for effecting cross feedingunder power, a disk fast to said driven shaft, and means for applying anadjustable friction to said disk to limit over-running of the shaft topermit cross feed under momentum to take place during the initialportion of the movement of the table after each reversal.

15. In a grinding machine having a reciprocatory work table, a crossfeed slide carrying the table and individual motors for operating thetable and slide, an operating member movable freely to a .predeterminedinitial position at the beginning of each cross feeding operation, poweroperated means for moving said member pro-4 gressively during theoperation of the cross feed motor, and a safety switch arranged to betripped by said member to cut 01! current to the cross feed motor whenthe cross seeding operation has exceeded a predetermined extent. I

16. In a grinding machine having a reciprocatory work table, a .crossfeed slide carrying the table and individual motors for operating thetable and slide, a rocker carrying a cam and ,arranged to occupy apredetermined initial position at the beginning of each cross feedingmove-' 1 ment of the feed slide, automatic mechanism for .starting thecross teed motor prior to each reversal of the table and for'initiatingrotation of vthe said rocker, and a normally closed switch arranged tobe tripped by saidcam after a predetermined interval of operation bysaid motor.

- 17. In a grinder having a' cross ieed,slide, a reciprocatory worktable thereon and motor driven operating mechanism for the slide andtable, a rocker on the cross reed slide oscillated the points ofreversal of table movement,.a cam movable directly by the rocker, aswitch in the cross feed circuit located adjacent to the cam and havinga plunger engaged thereby whereby the cross feed operating mechanism isthrown into action prior to and in anticipation of each reversal oftable movement, and means on the cross feed slide for adjusting therelative positions of the cam and switch whereby the extent 5 of crossfeeding movement may be regulated while the machine is in operation.

18. In a grinder having a cross feed slide, a re-, ciprocatory worktable thereon and motor driven operating mechanism for the cross slideincluding 1

